Nuclear Biosphere

Thorium and the Molten Salt ‘Nuclear’ Reactor

Most people know what uranium is but very few people know what thorium is. I have written about thorium several times in the past and about how China and India have invested substantial effort into developing thorium as a nuclear fuel to generate electricity for their respective countries. The question to ask is when will other countries invest in thorium reactors? Well, several countries in Europe have finally added thorium to the energy debate but the United States Government (NRC) is still sitting on the sidelines, considering it was the United States National Labs that discovered the potential of this safe, clean and abundant energy resource.

Back during the Manhattan Project of the 1940’s, Dr. Alvin Weinberg designed two different types of nuclear reactors to produce the plutonium for the atom bomb to use against Germany and Japan. The uranium reactor produced bomb grade plutonium and the thorium reactor did not. Therefore, thorium as a bomb source was set aside by the Manhattan team until after the WWII, when Dr. Weinberg took another look at it for an energy source to generate electricity.

The difference between the two reactor designs by Dr. Weinberg was in how the reactor was control with a coolant; water vs. molten salts. The light water reactor (LWR) was a perfect design for ships because of the abundance of water to cool the reactor. The Navy immediately commissioned it for its submarine fleet and later for its aircraft carrier fleet. Not to be outdone by the Navy, the Air Force commissioned Weinberg to build a nuclear bomber engine that didn’t have access to water. Luckily the ICBM came along and this foolish notion of a nuclear bomber was set aside.

What Dr. Weinberg had now was a working model of a small molten salt reactor at his Oak Ridge National Lab facility in Tennessee. With additional funding from the Atomic Energy Commission, Dr. Weinberg and his team of chemist and engineers scaled up the reactor design and successfully tested it for four years. Unfortunately, the Government had previously decided to fund an upscale version of the LWR (the ship engine) for use on land surface. That is why you always see a nuclear power plant next to a river or shoreline of a large lake or ocean. It needs the water as a coolant to control the fission reaction within the reactor vessel (it gets very hot).

Well, 450 LWRs later (worldwide and growing), many nations have decided to re-address the thorium molten salt reactor for several reasons, starting with cost. Over the last few decades, the LWR has become extremely expensive to build because of all the redundant safety requirements. Today the LWR is the safest energy source on record even with its three accidents over the last 5 decades with only 40 direct deaths all at Chernobyl. The other two accidents; Three Mile Island in PA and Fukushima in Japan had zero direct deaths caused by radiation exposure when they had their meltdowns.

However, the economies of scale for large centralized nuclear power plants has lost its advantage to smaller array scaled decentralized power units based on the thorium MSR designs. The MSR is self regulated (auto-shut down) and will not melt down (already liquid) while it consumes all the nuclear fuel (no waste storage) and takes up a very small environmental footprint (no CO2) all while operating underground (no visible cooling towers). What’s not to like about that?

There are also by-products and by-uses of a super high temperature liquid reactor design. For by-products there are several medical therapeutic radioisotopes that are created in the fission process that can be chemically isolated and extracted from the liquid fuel source.

For example (this will be techie), thorium-229, a decay element from thorium-232, can be harvested and through its decay chain provide bismuth-213. One Bi-213 atom can kill a cancer cell made up of about 100 trillion atoms. Fighting cancer with targeted alpha therapy will minimize “collateral” damage to the patient, since an alpha particle can only affect the adjoining two or three cells from its point of emission. This avoids the unpleasant consequences of typical chemotherapy, like hair loss and nausea.

Thorium (Th-232), which is available everywhere on earth and the moon is non-fissionable. When it is bombarded by a neutron inside a MSR device it is transformed into uranium-233, which is fissionable. The fission of U-233 will produce approximately 35 different elements as fission products in varying quantities. These elements include xenon, neodymium, molybdenum, and zirconium to name a few. Xenon is used by NASA for deep space travel as a propellant energy source for its ion engines.

One of the by-uses of the MSR is from the extreme heat that it can generate. Any industry that requires extensive heat for processing like; cement, aluminum and steel to name a few, can eliminate the use of coke and coal (dirty stuff) to heat their furnaces. Natural gas is a cleaner alternative to coal, but nuclear is completely clean (no CO2 or other polluting gases, like methane).

Several countries with arid ecosystems are currently using natural gas as an energy source to operate their desalination water plants. A small MSR will provide a cleaner and more efficient energy source to replace fossil fuels in the future for massive water desalination requirements. There is a critical need for more clean water to provide for the increasing world population and the electrification of the world at the same time. The most efficient and cleanest way to do that is with nuclear energy, specifically the MSR.